(a) Technical Field
The present invention relates to a control device and a control method for improving a voltage utilization ratio of an inverter for a green car, and more particularly, to a control device and a control method for improving a voltage utilization ratio of an inverter for a green car, which can improve the output and efficiency of a motor system and enhance vehicle fuel efficiency by improving the voltage utilization ratio of the inverter for controlling a driving motor of the green car.
(b) Description of the Related Art
As is known in the art, green cars including an electric vehicle (EV), a hybrid electric vehicle (HEV), a fuel cell electric vehicle (FCEV), and the like use electric motors as driving sources for vehicle driving.
In particular, a motor is driven by converting DC power stored in a main battery of a vehicle into three-phase AC power using an inverter, and the driving power of the motor is transmitted to driving wheels, thereby driving the vehicle.
In a motor system including a motor that is a driving source of a green car and an inverter, the inverter is generally configured with a plurality of insulated gate bipolar transistors (IGBTs). The inverter converts a DC voltage supplied from a battery through switching in response to a pulse width modulation (PWM) signal and supplies the converted voltage as a phase voltage for driving the motor.
The inverter acts as a motor controller, and controls operation of the motor by outputting a final PWM signal using a torque command signal applied from a hybrid control unit (HCU), a battery voltage state applied from the battery, and motor speed information applied from the motor.
However, in above-described conventional method, there is a disadvantage in that an input DC voltage Vdc input to the inverter is used in only a linear section, and therefore, any efficiency and output improvements of the motor system are limited.
In particular, when there is generated a voltage (output AC voltage of the inverter) incapable of being linearly output with respect to the input DC voltage of the inverter, the output of the inverter is limited so that only a linear output is generated. Therefore, the efficiency and output of the motor system are limited.
When the input current of the motor is controlled by improving a voltage utilization ratio of the inverter in a situation in which the output of the inverter is controlled using the conventional method, the motor control stability in a partial region is disadvantageous.